Along with the improvements of people's living standard, rates of diseases caused by unreasonable dietary structure are increasing too. Diabetes currently becomes a common disease to middle aged and elderly people, and even to young people. For the prevention of diabetes, it is necessary to control a daily intake of sugar within a reasonable range. Fruits and vegetables, especially the fruits, are foods having a relatively large sugar content, so people is required to pay attention to these foods. However, it is currently impossible to acquire the sugar content of the fruits and vegetables conveniently and accurately.